So I got Affinity Designer with the intention of transitioning away from PS for my work. I do art for videogames and a major aspect of that is specialized texture maps that use individual color channel information for game rendered lighting effects and masks. This often means I directly manipulating the color channels to either pack three grayscale maps into one file, or to edit a normal map (which uses RGB for vertical, horizontal, and forward lighting information).
I noticed pretty quickly that color channel options don't exist in Designer, and I was wondering if that was a feature you were planning to add? Without that ability I find myself unable to complete most tasks.